The second-seeded Argentine, last year's runner-up, used a single break in each set to overcome Monfils, who showed flashes of his unpredictable genius but not enough consistency to survive Del Potro's booming serve and barrage of accurate ground strokes.

The 2009 U.S. Open champion broke Monfils on the Frenchman's first service game and was only seriously tested once on his own serve, in the ninth game, when Monfils used his trademark return-everything scrambling game to force a break point that he failed to convert.

It was a similar story in the second set, with Monfils producing the highlight-reel shots but unable to break Del Potro and eventually losing his serve to love in the eighth game.

In the day's final match, Jarkko Nieminen took just an hour to cruise past David Goffin 6-0, 6-0. It was only the second "double bagel" in the tournament's history and the first since 1987.